Monoamine or polyamine reacted with polyepoxide/monoamine or polyamine precursor, epoxy resin and epoxide thinner

ABSTRACT

A curing agent for epoxy resins comprises: 
     a) a reaction product of at least one polyalkylene polyether monoamine and/or polyamine with a polyepoxide and optionally, a monoepoxide to obtain an epoxide group-containing precursor, the precursor further reacted with a primary monoamine and/or a primary or secondary polyamine in at least a 10% molar excess relative to the epoxide groups of the precursor, the reaction product being substantially free of non-reacted amines; 
     b) an amine-terminated adduct of an epoxy resin and a primary monoamine and/or a primary or secondary polyamine being substantially free of non-reacted amines; and 
     c) an amine-terminated adduct of an epoxide group-containing reactive thinning agent and a primary monoamine and/or a primary or secondary polyamine being substantially free of non-reacted amines, 
     wherein the epoxy resin of component b) and epoxide group-containing reactive thinning agent of c) are added to the epoxide group-containing precursor of component a) before the reaction with the primary monoamine and/or primary or secondary polyamine, and the sum of the primary monoamines and/or primary or secondary polyamines in a), b) and c) are reacted jointly with the epoxide group-containing components.

PRIOR APPLICATION

This application is a division of U.S. patent application Ser. No.09/813,179 filed Mar. 20, 2001, now U.S. Pat. No. 6,410,658.

The invention relates to curing agents for epoxide compounds, which areemulsifiable and/or soluble in water and which are preferably employedin the production of aqueous epoxy resin emulsions or dispersions.

From EP-B 0 387 418 are known water-emulsifiable curing agents for epoxyresins, which, at good property profiles of the cured products have lowviscosity, bright color and good emulsifying effects. These curingagents are produced by conversion of polyalkylene polyether monoaminesand/or diamines and/or polyamines with an average molecular weight of148 to 5000, with di- and/or polyepoxide compounds, if appropriate afterreaction or in mixture with monoepoxide compounds, conversion of thethus obtained epoxide group-containing precursor with a primary orsecondary mono- and/or di- and/or polyamine, wherein the secondary aminehas at least two secondary amino groups and the amine or amine mixtureis used in such quantities that the reaction-capable epoxide groups havea ratio of 1:2 to 1:10 to the hydrogen atoms on the nitrogen. But theystill have various shortcomings: due to their content of free amine,they tend to discolor and readily form carbamates, which becomesnoticeable during their application in coating means by their degradedinterlayer adhesion. But especially in the emulsion with water and epoxyliquid resin they do not indicate the end of the spreadable or workablelife. But precisely this property is highly important since iteliminates erroneous application.

This indication of the workable life is to be understood as follows: anaqueous emulsion applied on a substrate dries. Therein the emulsion andthe remaining droplets of the nonaqueous phase, which ideally containsresin and curing agent in the proper mixing proportions, form a filmbefore the film is chemically cured. The time interval between theproduction of the emulsion and that point in time, starting when filmscan no longer be formed from the emulsion, or films are formed which aredefective in their properties, is known as the workable life. Thisworkable life can in certain cases be shorter than the processing time,i.e. that time in which the emulsion can be applied onto a substrate. Itis therefore advantageous, if a binding means systems indicates the endof the workable life thereby that at the end of the workable life, theviscosity of the emulsion already increases so strongly that processingis no longer possible.

Water-emulsifiable curing agents for epoxy resins, which have a workablelife indication, are known from EP-A 0 821 021. These are reactionproducts of aliphatic polyols with epoxy resins, which are subsequentlyconverted with polyamines. The reaction of polyols with resins onlytakes place at markedly increased temperature under catalysis. Throughthe homopolymerization of the resin, products are generated withincreased viscosity and the resin must be used in large excessquantities. This degrades the emulsifiability of the correspondinglyproduced adducts.

It is therefore the task of the invention to provide water-emulsifiablecuring agents for epoxy resins which have the same good property profileas the curing agents known from EP-B 0 387 418, but which indicate theend of the workable life. It is furthermore a task of the invention toprovide such curing agents substantially free of low-molecular amines,but which, nevertheless, are not dark in color and which are thus alsosuitable for the production of white coatings.

The solution of the task takes place through curing agents according toclaims 1 and 2 and through processes for their production according toclaims 3 and 4. These curing agents are suitable, in particular togetherwith one or several epoxide compounds and water as well as, ifappropriate, fillers and additives, such as for example pigments,antifoaming agents or deaerating agents, for the production of lacquersand varnishes, coatings and covering layers, as well as as additives forhydraulic binding agents. These curing agents are further suitable, inparticular together with one or several epoxide compounds as well as, ifappropriate, fillers and additives, such as for example, pigments,defoaming agents or deaerating agents for the production of sealing andadhesion substances as well as of flexible preforms, sheet materials andlaminates and are used for these application purposes.

Since in the production of the curing agents according to EP-B 0 387 418in the second reaction step only the complete conversion of the epoxidegroups with amino groups and not a curing reaction is desired, thesecond conversion must take place at a molar amine excess. The curingagents, consequently, comprise free amines which lead to the propertieswhich were listed in the introduction as being undesirable. It has beenfound that these non-converted amines can be removed from the reactionmixture by distillation, without the previously favorable properties ofthe amine-free curing agents being degraded if, for the second reactionstep, amines are used which can be distilled without decomposition. Thisdistillation is technically not simple since the reaction mixture mustbe heated to relatively high temperatures and, moreover, foams intenselyduring distillation under vacuum.

It is, in particular, surprising that in this separation of the aminesby distillation only minimum discolorations occur of the curing agentsremaining as residue in the distillation and substantially free ofprimary or secondary mono- and/or di- and/or polyamines, and thatthrough this process step the important property of workable lifeindication is attained.

But this product by itself is not suitable as curing agent forwater-emulsifiable epoxy resin systems since, due to the high content ofalkylpropylene oxide units, coatings are formed whose water resistancedoes not meet quality requirements. Moreover, for the same reason,through-curing is considerably delayed and the final strength of thefilms is too low.

It was found that these disadvantages are overcome if the curing agent,in addition to these conversion products (component a), comprise thefollowing components:

the amine-terminal adduct of an epoxy resin and a primary or secondarymono- and/or di- and/or polyamine, wherein the secondary amine has atleast two secondary amino groups and the adduct is substantially free ofnon-converted amines (component b), and the amine-terminal adduct of areactive thinning agent and a primary or secondary mono- and/or di-and/or polyamine, wherein the secondary amine has at least two secondaryamino groups and the adduct is substantially free of non-convertedamines (component c).

These three components a, b and c, in the curing means according to theinvention are comprised in a weight ratio of 10 to 60 to 5 to 85 to 5 to85.

Consequently, curing agents having a substantially improved propertyspectrum are obtained through the distillation of the excess,non-converted mono-, di- or polyamines following the synthesis of theemulsifying agent component a, and through the combination with at leasttwo different epoxide-amine adducts, also freed by distillation ofnonconverted mono-, di- or polyamines.

These are curing agents which in their aqueous emulsion with epoxyliquid resins are resistant to alkali, have low viscosity, inherentlight color, and low toxic potential, which do not tend to formcarbamate, which can be emulsified in water simply with toolsappropriate to building sites, and which, in mixtures with thecorresponding stoichiometric proportions of epoxy resins and, ifappropriate, reactive thinning agents and water, preferably with a watercontent of 40-60% relative to the organic substance, cure rapidly evenat low temperatures, wherein the corresponding emulsions have a clearlydetectable workable life end and the cured coatings are water-resistant,bright and exhibit a low degree of yellowing.

The curing means show a very high reactivity with corresponding shortworkable lives. They are therefore only suitable for use in processingmethods by machine, in which short processing times are permitted oreven desired. The reactivity of the curing means must be appropriatelyreduced for manual processing methods. This is attained thereby that thecuring means are additionally converted with up to 50 mol %, relative tothe amino groups, of reactive thinning agents.

It was furthermore found that, if in the production of curing meansanalogous to those known from EP-B 0 387 418, in the first conversion aspolyalkylene polyether amines are also used polyalkylene polyethermonoamines and/or diamines and/or polyamines based on ethylene oxide(polyethylene polyether amines) as well as also polyalkylene polyethermonoamines and/or diamines and/or polyamines based on propylene oxide(polypropylene polyether amines) and/or polyalkylene polyethermonoamines and/or diamines and/or polyamines based on butylene oxide(polybutylene polyether amines), the resulting curing means in emulsionswith epoxy resins, in particular in filled systems, have significantlyimproved brightness after curing. It is therein insignificant whetherthese polybutylene polyether, polypropylene polyether, and/orpolyethylene polyether amines are converted sequentially with theepoxide compounds or are previously mixed with one another.

Conversion with the di- and/or polyepoxide compounds, which, ifappropriate, can also take place after the reaction or in mixtures withmonoepoxides, is conducted with the methods known from EP-B 0 387 418,as a rule by conversion of the co-reactants with one another attemperatures in the range from 20 to 120° C., preferably in the rangefrom 50 to 90° C. and by maintaining the reaction mixture forapproximately 1-5 h at a temperature in this range. Separation bydistillation of the amines, not converted in the second reaction step,takes subsequently place.

The quantitative ratio of the sum of the polyalkylene ether amines tothe di- and/or polyepoxide compounds is selected such that the obtainedproducts comprise at least one free epoxide group per molecule, i.e. thequantity of epoxide compounds with more than one epoxide group permolecule is selected such that the ratio of the hydrogen atoms bound tonitrogen, which possibly remain after the conversion with monoepoxidecompounds and which are capable of reacting with epoxide groups, to theepoxide groups of di- or polyepoxide compounds is in the range from1:1.4 to 6.

As the amine components for this first reaction step serve commerciallyavailable polyalkylene polyether monoamines and/or diamines and/orpolyamines, preferably such based on ethylene oxide (polyethylenepolyether amines) and based on propylene oxide (polypropylene polyetheramines). These polyalkylene polyether amines have average molecularweights of 148 to 5000, preferably between 400 and 2000. Thequantitative ratio of the polyethylene polyether amines to thepolypropylene polyether amines are each in the range of 5:95 to 95:5. Tothis can be added up to 10% polybutylene polyether amines.

Since polyethylene polyether amines are more hydrophilic thanpolypropylene polyether amines and polybutylene polyether amines, it ispossible, through the purposeful and specific combination in suitablemixing ratios of the different polyalkylene polyether amines to adjustthe HLB value of the curing means obtained after mixing the componentsa, b, and c as well as, if appropriate, further compounds, to react withpreferably monofunctional epoxide, compounds such that at differentquantitative ratios of the individual components an optimum over wideranges is attained with respect to emulsifiability and water resistanceof the cured coating.

As epoxide components for the first reaction step, as well as for theproduction of component b, serve primarily epoxide compounds with morethan one epoxide group per molecule. To diminish the amine functionalityof the polyalkylene polyether amines, epoxide compounds can additionallybe used having only one epoxide group per molecule unit.

These are aliphatic, araliphatic, cycloaliphatic, aromatic orheteroaromatics-comprising compounds with one epoxide group permolecule. These products are referred to as so-called reactive thinningagents.

Examples of these are butyl-, hexyl-, phenyl-, butyl phenyl- or cresylglycidyl ethers. But other monoglycidyl compounds can also be used, suchas glycidyl esters, amines, -thioethers, -amides, -(iso)cyanates,aralkylene oxides and glycidylated fatty alcohols.

Of the large number of polyfunctional epoxide compounds comprising morethan one 1,2-epoxide group in the molecule, will be listed: the epoxidesof polyunsaturated hydrocarbons (vinyl cyclohexene, dicyclopentadiene,cyclohexadiene, cyclododecadiene, cyclododecatriene, isoprene,1,5-hexadiene, butadiene, polybutadienes, divinylbenzenes and the like),oligomers of epichlorohydrin and the like, epoxide ethers of multivalentalcohols (ethylene-, propylene- and butylene glycols, polyglycols,thiodiglycols, glycerine, trimethylol propane, pentaerythritol,sorbitol, polyvinyl alcohol, polyallyl alcohol and the like), epoxideethers of multivalent phenols (resorcine, hydroquinone,bis-(4-hydroxyphenyl)-methane, bis-(4-hydroxy-3-methylphenyl)-methane,bis;(4-hydroxy-3;5-dibromophenyl)-methane,bis-(4-hydroxy-3,5-difluorophenyl)-methane,1,1-bis-(4-hydroxyphenyl)-ethane, 2,2-bis-(4-hydroxy-phenyl)-propane,2,2-bis-(4-hydroxy-3-methylphenyl)-propane,2,2-bis-(4-hydroxy-3-chlorophenyl)-propane,2,2-bis-(4-hydroxy-3,5-dichlorophenyl)-propane,2,2-bis-(4-hydroxy-3,5-dichlorophenyl)-propane,bis-(4-hydroxyphenyl)-phenyl methane, bis-(4-hydroxyphenyl)-diphenylmethane, bis-(4-hydroxyphenyl)-4′-methylphenyl methane,1,1-bis-(4-hydroxyphenyl)-2,2,2-trichloroethane,bis-(4-hydroxyphenyl)-(4-chlorophenyl)-methane,1,1-bis-(4-hydroxyphenyl)-cyclohexane,bis-(4-hydroxyphenyl)-cyclohexylmethane, 4,4′-dihydroxydiphenyl,2,2′-dihydroxy diphenyl, 4,4′-dihydroxydiphenylsulfone as well as theirhydroxy ethylethers, phenol formaldehyde condensation products, such asphenol alcohols, phenol aldehyde resins and the like, S and N-containingepoxides, (N,N′-diglycidyl aniline, N,N′-dimethyldiglycidyl-4,4-diaminodiphenyl methane) as well as epoxides which have been produced frompolyunsaturated carboxylic acids or monounsaturated carboxylic acidesters of unsaturated alcohols, glydicyl esters, polyglycidyl esters,which can be obtained by polymerization or mixed polymerization ofglycidyl esters of unsaturated acids or from other acidic compounds(cyanuric acid, diglycidyl sulfide, cyclic trimethylene trisulfone ortheir derivatives and the like).

Preferred epoxide compounds are polyphenol glycidyl ethers liquid andsolid at ambient temperature, for example the reaction products ofepichlorohydrin and bisphenol A or bisphenol F. Such epoxy resins havean epoxy equivalent of 160->700. The above polyfunctional epoxidecompounds, this expression also includes the term epoxy resin, can beconverted according to the present method alone or mixed, if appropriatein the presence of solvents. They can also, as already discussed above,be used in mixtures with monoepoxides.

As amine components for the second reaction step, as well as for theproduction of components b and c, serve commercially availablelow-molecular monoamines, diamines, and polyamines, which can each beused alone or mixed with one another.

The selection of amines and their mixtures can take place as desiredwithin broad ranges. However, participating in the conversion must beamines with at least one primary amino group or, when using secondaryamines, such with at least two secondary amino groups, in order toensure that the desired end product has at least one free primary orsecondary amino group per molecule. In addition, it must be possible todistill these amines without decomposition occurring.

Examples of monoamines are therefore butylamine, cyclohexylamine,aniline or benzylamine, while secondary monoamines at best are used inexcess relative to functional groups (epoxide groups) to reduce thefunctionality of the precursor, to decrease the viscosity or, ifappropriate, to introduce catalytic groups.

As di- and polyamines can be used aliphatic, araliphatic,cycloaliphatic, aromatic or heterocyclic di- and/or polyamines, whichcan be distilled without decomposition.

Examples are: ethylene diamine, diethylene triamine, triethylenetetramine, tetraethylene pentamine, 1,2-diamino propane, 1,3-diaminopropane, 1,2-, 1,3- and 1,4-diamino butane, 3-(2-aminoethyl)-aminopropylamine, N,N′-bis(3-aminopropyl)-ethylene diamine, 1,2-diaminocyclohexane,1,3-diaminocyclohexane, 1,4-diaminocyclohexane, N-amino ethylpiperazine, N-aminopropyl piperazine, N-aminobutyl piperazine, phenylenediamines, xylylene diamines and isophorone diamine or mixtures of theseamines. The quantity of the amine or amine mixture to be used should beproportioned such that they are used at least in a 10% molar excessrelative to the epoxide groups of the precursor. This excess can beunlimited for reasons of chemical consideration. But since the excessamines must again be distilled off, for reasons of economics it isadvisable to limit the excess. In general, the amines are therefore usedin a 10 to 100% molar excess relative to the epoxide groups of theprecursor.

The second reaction step takes place such that the product obtained inthe first reaction step is mixed directly with the selected amine oramine mixture and is treated for several hours (1-5 h) at a temperaturein the range from 20 to 120° C., in particular in the range from 50 to90° C. Subsequently, the free, non-converted amines are separated bydistillation, preferably under vacuum.

The production of the amine-terminal adducts of an epoxy resin and aprimary or secondary mono- and/or di- and/or polyamine takes place in amanner known per se by conversion of the corresponding products with oneanother. As the epoxy resin can therein be used all previously listedepoxide compounds with more than one epoxide group per molecule and, asthe amine component, all previously listed low-molecular di- andpolyamines such as aliphatic, araliphatic, cycloaliphatic, aromatic orheterocyclic di- and/or polyamines can be used, which can be distilledwithout decomposition. Here also the amines are used at least in a 10%molar excess relative to the epoxide groups of the epoxy resinsemployed. For chemical considerations this excess can be unlimited. Butsince the excess amines must again be distilled off, it is advisable foreconomic reason, to limit the excess. In general, the amines aretherefore used in a 10 to 100% molar excess relative to the epoxidegroups of the epoxy resins employed.

The production of the amine-terminal adducts from a reactive thinningagent and a primary or secondary mono- and/or di- and/or polyamine alsotakes place in a manner known per se by conversion of the correspondingproducts with one another. As reactive thinning agents can therein serveall previously listed epoxide compounds with one epoxide group permolecule, such as aliphatic, araliphatic, cycloaliphatic, aromatic orheteroaromatics-containing compounds with one-epoxide group permolecule. Examples are butyl, hexyl, phenyl, cresyl, butylphenyl ornonylphenyl glycidyl ethers. But other monoglycidyl compounds can alsobe used such as glycidyl esters, -amines, -thioethers, -amides,-(iso)cyanates and aralkylene oxides as well as monofunctionalglycidylated fatty acids, glycidylated fatty alcohols or alsopolyfunctional reactive thinning agents such as glycidyl ethers based onmultivalent alcohols such as butanediol, hexanediol, pentaerythritol ortrimethylol propane. As the amine component can also be used forcomponent c all previously listed low-molecular di- and polyamines suchas aliphatic, araliphatic, cycloaliphatic, aromatic or heterocyclic di-and/or polyamines which can be distilled without decomposition. Theamines are here also used in a 10% molar excess relative to the epoxidegroups of the epoxy resins used. For chemical considerations this excesscan be unlimited. But since the excess amines must again be distilledoff, it is advisable for economic reason, to limit the excess. Ingeneral, the amines are therefore used in a 10 to 100% molar excessrelative to the epoxide groups of the epoxy resins employed.

The curing agent components a, b and c according to the invention caneach be produced separately and, after completed production, can bemixed with one another for the final curing agent formulation.

But the curing means according to the invention can also be producedsuch that components a, b and c are mixed each with their fractions ofexcess amines and, subsequently, the nonconverted mono-, di- orpolyamines, can be separated by distillation from the mixture. If for aand b the same epoxide compound is used, this can be presented at thebeginning in its entire quantity.

A further simplification of the production of the curing means accordingto the invention can be attained thereby that, after the production ofthe precursor of component a, the epoxy resins for component b and thereactive thinning agents for component c are added to the precursor andthe sum of all mono-, di- and/or polyamines to be used and the lastconversion as well as also the processing by distillation of all threecomponents takes place jointly.

The amine-terminal curing means produced according to the invention,which are present as an emulsion or a solution, are mixed, ifappropriate, with additional reactive curing agent components,commercially available auxiliary agents, such as, for example fillers,pigments, flow improving agents, antifoaming agents, deaerating agents,etc. as well as further substances known as auxiliary agents for curingmeans for epoxy resins, such as for example solvents, accelerators, etc.with epoxide compounds, in particular epoxy resins with at least twoepoxide groups per molecule unit in equimolar ratios of amino andepoxide groups and, if appropriate, after the addition of water andwhile being agitated intensively are dispersed or emulsified, applied asemulsions or dispersions and allowed to cure.

Depending on the requirements, the curing takes place at lowtemperatures down to approximately 0° C. within 3 to 72 hours after themixing or at increased temperatures.

The curing means produced thus are subsequently diluted with water ifthey are intended to be used in water-emulsifiable systems. Ifappropriate, a quantity of monofunctional reactive thinning agents isalso added in order to adjust the reactivity of the system by blockingprimary amino groups. The quantity depends on the desired reactivity(workable life) and the targeted HLB value of the curing means.Subsequently follows again dilution with water, such that an emulsionand/or solution with a water content of preferably 40% is obtained. Suchemulsions are in particular suitable for the production of sealings orprimers as well as for decorative finishing coatings based on epoxyresins.

To the curing means according to the invention can be added furtherepoxy resin curing agents, known per se, in particular amine-terminalpolyalkyl ethers, primary long-chain monoamines or amine-terminalbutadiene-acrylonitrile copolymerisates as well as metal complexcompounds. As a rule, these curing agent mixtures are also emulsifiablein water.

The curing means according to the invention and the curing agentmixtures comprising them can, furthermore, be combined in a manner knownpe se with additional conventional additives, accelerators, and reactionretarding agents. Such curing agent mixtures can also be emulsified inwater.

EXAMPLES

Quantitative specifications in the examples are each given in parts byweight.

The abbreviation AT signifies ambient temperature.

The abbreviation equ. signifies equivalent.

Example 1 Production of the Emulsifier Component

To 130 parts of a bisphenol F diglycidyl ether with an epoxy equivalentof 172 g/equivalent (Rüitapox® 0161), heated to 100° C., are added underintensive agitation and over a period of 2 hours 94 parts polyalkylenepolyether monoamine based on ethylene oxide with an average molecularweight of 1000 (Jeffamine® M-1000) and 57 parts polyalkylene polyethermonoamine based on propylene oxide with an average molecular weight of600 (Jeffamine® M-600) (molar ratio epoxy: amine of 2:1). After areaction time of 2 hours at 100° C. this precursor is added over aperiod of 2 hours under nitrogen and intensive agitation to 110 parts oftriethylene tetramine and converted for 2 hours at 80° C. (ratio ofepoxy: amine=1:2 mol or 1:12 equivalents). The reaction mixture issubsequently slowly heated to 250° C. under vacuum and the nonconvertedtriethylene tetramine is distilled off. Obtained is a product having aviscosity at 25° C. of 30000 mPas, an amine equivalent of 179 g/equ. anda Gardner color number <3.

Example 2 Production of the Epoxy Resin Adduct

To 145 parts of triethylene tetramine (TETA) are added over a period of2 h at 80° C. 85.2 parts of bisphenol F diglycidyl ether with an epoxyequivalent of 172 (Rütapox® 0161) (ratio of epoxy:amine:1:2 mol or 1:12equivalents). The secondary reaction takes place for 2 h at 80° C. Thedistillation of the excess amine subsequently takes place at 250° C. and50 mbar.

The obtained final product has a viscosity at 80° C. of 10000 mPas, anamine equivalent of 64 g/equ. and a color number according to Gardner of<3.

Example 3 Production of the Reactive Thinning Agent Adduct

Analogously to Example 2, 84.7 parts phenyl glycidyl ether and 122.4parts para-t-butyl phenyl glycidyl ether are converted with 320 partsTETA (ratio of epoxy:amine:1:2 mol or 1:12 equivalents). The secondaryreaction is carried out for 2 h at 80° C. Subsequently the distillationof the excess amine is carried out at 250° C. and 50 mbar.

The obtained final product has a viscosity at 25° C. of 10000 mPas, anamine equivalent of 68 g/equ. and a color number according to Gardner of<3.

Example 4 Formulation of the Curing Agent

To a mixture of 336 parts emulsifier component from Example 1, 367.5parts of the adduct from Example 2 and 367.5 parts of the adduct fromExample 3 are added successively at 90° C. 114 parts phenyl glycidylether and 75 parts p-tert. butylphenyl glycidyl ether. After a reactiontime of 2 h at 90° C., 700 parts dist. water are added. The obtainedcuring means has a viscosity at 25° C. of 5000 mPas, an amine equivalentof 200 g/equ. and a color number after Gardner <3.

Example 5 Production and Application of a Ready-to-use Emulsion

After mixing 32 parts of the curing means with 31 parts of areactive-thinned liquid epoxy resin (basis bisphenol A, epoxy equivalent190 g/equ.) and 37 parts water, this mixture has a workable life atambient temperature of approximately 120 minutes. When a thin layer ofthis emulsion is applied onto a substrate, rapid film formation takesplace. The end of the workable life is clearly detectable by a strongincrease of the viscosity. The cured film has a lustrous brightness(175% at a measuring angle of 20°). The pendulum hardness (after König)after 24 h is 100 s at ambient temperature, and after 7 days it is 200 sat ambient temperature.

What is claimed is:
 1. A curing agent for epoxy resins comprises: a) areaction product of at least one polyalkylene polyether monoamine and/orpolyamine having a molecular weight of from 148 to 5000 with apolyepoxide and, optionally, a monoepoxide, in a ratio of aminehydrogen, optionally remaining after reaction with the monoepoxide, andepoxide groups of the polyepoxide of from 1:1:14 to 1:6 to obtain anepoxide group-containing precursor, the precursor further reacted with aprimary monoamine and/or a primary or secondary polyamine in at least a10% molar excess relative to the epoxide groups of the precursor, thereaction product being substantially free of non-reacted amines; b) anamine-terminated adduct of an epoxy resin and a primary monoamine and/ora primary or secondary polyamine being substantially free of non-reactedamines; and c) an amine-terminated adduct of an epoxide group-containingreactive thinning agent and a primary monoamine and/or a primary orsecondary polyamine being substantially free of non-reacted amines,wherein the epoxy resin of component b) and epoxide group-containingreactive thinning agent of c) are added to the epoxide group-containingprecursor of component a) before the reaction with the primary monoamineand/or primary or secondary polyamine, and the sum of the primarymonoamines and/or primary or secondary polyamines in a), b) and c) arereacted jointly with the epoxide group-containing components.
 2. Thecuring agent of claim 1 wherein the polyalkylene polyether monoamineand/or polyamine is based on ethylene oxide or butylene oxide.
 3. Amethod for the production of the curing agent of claim 1 comprising: i)mixing and reacting the polyalkylene polyether monoamine(s) and/orpolyamine(s) with the polyepoxide, and optionally, the monoepoxide, toobtain the epoxide group-containing precursor, ii) blending theprecursor with the epoxy resin of component b) and epoxidegroup-containing reactive thinning agent of component c) to form amixture, iii) reacting the mixture with a primary monoamine and/orprimary or secondary polyamine being substantially free of non-reactedamines, and iv) distilling the mixture to remove non-reacted monoaminesand/or polyamines to form the curing agent.
 4. The method of claim 3wherein the polyalkylene polyether monoamine and/or polyamine is basedon ethylene oxide or butylene oxide.